#

# break a range list down into its components, unrolled
# (translates "1,3,9-12,10-" into "1 3 9 10 11 12 10 11 12")
#
range_to_list ()
{
        local -i len i

        local portion dash

        local -a resultlist

        local arg=$1 max=$2

        local rangepattern='^([[:digit:]]*)(-{0,1})([[:digit:]]*)$'
        local rangedelimiter=','
        local shellfalse=1

        # although these are numbers, they must not have the
        # integer attribute set because otherwise a null one
        # expands to 0 and we cannot differentiate between
        # that and lack of given arg
        #
        local start end

        # two args is the only format and is required
        #
        (($# != 2)) && return $shellfalse

        # iterate through each delimiter-separated list given
        #
        while [[ "$arg" ]]
        do
                # strip out the first delimited portion for this loop
                #
                eval portion=\${arg%%${rangedelimiter}\*}
                len=${#portion}
                arg=${arg:len+1}

                # the special case of field 0 is a
                # substitute for "all fields" in the rangelist
                #
                [[ "$portion" == '0' ]] && portion="1-$max"

                # impose a rewrite on the given ranges into
                # a standard range form:
                #
                #     `start-' -> `start-max'
                #     `number' -> `number-number'
                #     `start-end' -> no change
                #
                # iteration logic can then assume only the
                # `start-end' form is used
                #
                [[ $portion =~ "$rangepattern" ]] || return $shellfalse
                start=${BASH_REMATCH[1]}
                dash=${BASH_REMATCH[2]}
                end=${BASH_REMATCH[3]}

                if [[ "$dash" ]]
                then end=${end:-$max}
                else end=$start; dash='-'
                fi

                for ((i = start; i <= end; i++)); do
                        resultlist+=($i)
                done
        done

        echo ${resultlist[@]}
}

# vim:syn=sh:
# vim:syn=sh:ft=sh